The present invention relates to an inspection apparatus for flanged or curled open end parts of cans, and more particularly to an inspection apparatus for flanged or curled open end parts of cans wherein the inspection can be carried out continuously.
Hitherto, as inspection methods for flanged parts of deep drawn cans and curled parts of aerosol cans, made of metal plate such as tin plate, aluminum plate and tin free steel plate, there are known an air tester method and an optical tester method.
According to the air tester method, detection of defects is carried out as shown in FIG. 6. The procedure is explained by the following (a) to (e).
(a) An open end of a can 2 is pressed onto rubber material 37 on substrate 36 by a pusher 39 contained in a sealed tube 38. PA0 (b) Compressed air having a positive pressure of about 0.6 kg/cm.sup.2 is supplied continuously inside of the can through an air pipe 40. PA0 (c) If the can has a pin hole p, air leaks through the pin hole p and flows to the outlet of the inspection nozzle. PA0 (d) The air flow is detected via vibration of wire mesh 42 or differential pressure by a sensor 43. PA0 (e) The signal from the sensor 43 is transmitted to a detector 45 via an amplifier 44, and then the defect of flanged part 2a or curled part 2b is detected by the level of signal. PA0 (a) A can 2 is stuck onto rubber material 47 on substrate 46 by suction. PA0 (b) The can 2 is irradiated by a light source 48. PA0 (c) If the can 2 has any pin hole, light leaks through the pin hole. PA0 (d) The leaking light L is detected by a photo detector 49 such as photo multiplier tube, and then the defects of flanged part 2a or curled part 2b are detected. PA0 (a) a vertically arranged can feeding mechanism having a vertically arranged timing screw which horizontally arranges cans in line and intermittently transfers cans one by one and a non-contact sensor closely facing one end of a timing plate attached firmly on an infeed driving shaft which is connected to one end of timing screw with synchronously drivable condition via bevel gear, places cans, which are fed continuously on a can feeding station, one by one to the prescribed position in static magnetic field of inspection station, PA0 (b) a rotary mechanism which forcibly rotates cans, wherein the can is held in the prescribed position in the inspection station, and is supported horizontally by outside body thereof, without applying force in longitudinal direction, and with driving torque being directly transmittable, PA0 (c) a magnetic head closely facing a part of a flanged part of can which is rotated in the inspection station, PA0 (d) a discriminating circuit detecting cans with defects, wherein the magnetic head output signal, which indicates the inspected part condition, is transmitted to a wave form modification circuit which applifies and shapes the signal, and then the signal is compared with a standard signal stored previously, and PA0 (e) a rejector which rejects cans with defects during inspection by allowing them to fall by self-weight, by receiving a discriminating circuit operational signal which is controlled by a timing signal from the timing screw. PA0 (a) a feeding means which feeds cans continuously, PA0 (b) a holding means which removably holds a can fed by the feeding means, PA0 (c) an inspecting means which inspects a flanged or curled part of the can, PA0 (d) a locating means which keeps the sensor holders at a certain location relative to the flanged or curled part of can, PA0 (e) a discriminating means which discriminates if there is any defect in flanged or curled part by information from the inspecting means, and PA0 (f) a discharging means which discharges a can with defects at a prescribed position, and a can without defects at another prescribed position respectively.
According to the optical tester method, detection of defects is carried out as shown in FIG. 7. The procedure is explained by the following (a) to (d).
The suction, for example, can be done by making negative pressure inside of the can 2.
Since both conventional methods as mentioned above can display their ability when the flange part 2a or the curled part 2b of can 2 is stuck onto rubber material 37 or 47, they can only detect such defects as reach to the body of can 2. However, they cannot detect small cracks of the flanged part or curled part. Therefore, after the cans 2 are inspected by the air tester method and the like, all of them are visually inspected by specially arranged inspectors. However, oversight of defects easily occurs during visual inspection. Small defects, which are not discriminated by visual inspection, cannot be detected either. It takes too long to inspect the can by the visual inspection. In result, the visual inspection has become non efficient and the main bottleneck of can production line.
Japanese Examined Patent Publication No. 20977/1984 discloses an inspection apparatus for a flanged part of cans which solves the problems of the conventional tester methods by automatically rejecting cans with defects. Namely, it provides a flange crack tester for two piece can comprising;
According to the above-mentioned flange crack tester, high speed inspection can be realized without applying undue force to cans to be inspected.
However, it is obliged that the inspection becomes intermittent since the flanged part of the can is inspected by a fixed sensor in a condition that the revolution of can is stopped at the prescribed position and then the can is forcibly rotated. In addition, the number of sensor is one, therefore, the inspection efficiency is very low. In result, the apparatus has a defect that it cannot improve in the inspection efficiency of the can production line enough.
It is an object of the present invention to solve the above mentioned problems of the conventional inspection apparatus, i.e., to provide an inspection apparatus wherein visual inspection falls into disuse, the inspection for the flanged or curled part of cans can be carried out continuously without stopping cans, and the inspection efficiency is improved.